How long can a creditor keep a lien on a checking account? As of now it has been a year since they placed the lien on the account.

I am not familiar with a lien on a checking account, unless you are describing a garnishment. I would go to the court where the lien originated and ask for more information about the process. If the lien is, in effect, a garnishment, you may want to bank elsewhere. Has the lienholder been paid off? If so, the lien should be marked, "Satisfied", and thereby released.